In the Shadowrun Anarchy system, many of the game mechanics allow for the reroll of misses. None of the existing reroll mechanics in d20 support this. For example: Player (Mitch) rolls to attack with Firearms + Agility (10 total dice). He has a shadow amp that allows him to reroll up to 2 misses. Mitch rolls 10 dice (/roll 10d6>5): 5 6 3 2 2 1 4 5 4 6 . That would be 4 successes, 6 misses. Currently, he'd have to initiate a manual reroll of 2 dice (/roll 2d6>5). 1 5 . He got another hit, resulting in 5 successes. Currently in roll20, the reroll mechanics are: Basic Reroll: /roll 10d6>5r<4. This would not work as it would reroll all misses. Reroll once: /roll 10d6>5ro<4. Closer, but this would still reroll all misses once. Proposal: Reroll a number of dice once: /roll 10d6>5rr2,<4 (Rolls 10d6, counts 5&6 as success. Rerolls up to 2 misses [any dice that are 4 or less]). It would have to check to see how many misses there are and if the number of misses is less than the target, reroll only the number of misses, not the target.